The present invention relates to a fuel control for motor vehicle internal combustion engine systems in which a vehicle control system employs a fuel bucket scheduler operating in a circular queue segmented by a link list to reduce throughput without affecting firing order by dequeueing a link list for each bucket and recalculating phase and bucket number for each injector in a bucket.
Previously known fuel control systems have become more complicated as the number of inputs to which the scheduler responds multiplies the processing calculations required to generate timely control signals to the injector drivers. For example, some of the injectors for particular cylinders may be cut under certain operating conditions, like during cornering in a racing car or when a cut command is initiated as a response to a traction control system attempting to control the application of torque to a drive shaft, a wheel or the like. Moreover, when cylinders (i.e., injectors) have been cut, the operation of each cylinder may be affected by a phenomena such as boundary,layer depletion that may require a response such as wall wetting to reestablish normal fuel load conditions in a cylinder. For example, an injector may need to be turned on prior to its usual turn-on time so that the cylinder walls can be wet to restore the usual fuel conditions in the cylinder before firing the mixture in the cylinder.
Since the cylinders follow a particular firing order, a large quantity of information may need to be processed for maintaining proper operation of the cylinders before timely turn-on pulses in control signals are sent to the injector drivers under all of the operating conditions encountered by the vehicle and the vehicle control system. The previously known fuel control systems were not set up to minimize processing time or processing throughput for the multiple changing controls required for each of the injectors, particularly as the number of cylinders to be controlled are increased in an engine.
The present invention overcomes the above-mentioned disadvantages by providing a method and apparatus for delivering fuel to the injectors of an internal combustion engine according to a schedule that is adjusted throughout a variety of operating conditions with a minimum of chronometric or throughput loading. The method schedules a circular queue of a plurality of buckets defining a predetermined portion of a combustion cycle. Each bucket is defined by a combustion cycle interval and initiated by an event triggered interrupt (PIP). A combiner, for example, a linked list of pointers to a fueling information data storage sorts the cylinders in the buckets. An assigner designates cylinders as assigned to each bucket according to a predetermined logic determination and to an injector demand signal.
In a preferred embodiment, the number of buckets is selected as the number of cylinders firing within one firing sequence, for example, throughout a 720xc2x0 crankshaft rotation for a four cycle engine. The preferred embodiment may also be set up so that the link list normally assigns a cylinder to each bucket. Each bucket is initiated by the fuel scheduler PIP interrupt handler in which the link between the cylinder and the bucket is dequeued for processing of the cylinder for the next combustion cycle event. Nevertheless, the firing order remains intact because only the cylinders assigned to the bucket are processed for generating injector controls, for example, as to the phase for initiating firing of the injector within the bucket and the number of the bucket in which the firing is to occur, before a length of pulse or other demand signal is applied for the firing order in the queue. Accordingly, only a limited amount of information is processed at one time.
Moreover, such a processing can be handled in a short time without affecting the firing queue of the cylinder, enabling the link list to be requeued in the same firing order cycle. The cylinder is processed in the firing queue to change the length of the control pulse to the fuel injector in response to operating parameters, such as current air/fuel ratio, pre-calculated air/fuel values or the like. Once the phase of pulse initiation and pulse length due to demand have been determined, the figures are input to an injector driver, for example, by loading hardware registers in the driver, to control the operation of the injector or injectors at each cylinder.